1. Field of the Invention
The present invention generally relates to color linear sensors and, more particularly, to a color linear sensor having a dot-sequential sensor array in which photo sensors of three colors such as R (red), G (green), B (blue) or the like are sequentially arranged at the unit of pixels in a one-dimensional fashion.
2. Description of the Prior Art
Linear image sensors (hereinafter simply referred to as "linear sensor") have advantages such that they are small in size and low in electric power consumption. Hence, the linear image sensors are utilized in a wide variety of fields such as copy, facsimile image transmission, optical character recognition (OCR), pattern recognition, measurement and so on. As color copies are popularizing recently, color linear sensors are often utilized.
FIG. 1 of the accompanying drawings shows a structure of a conventional color linear sensor of R, G, B line-sequential output type having three sensor arrays.
As shown in FIG. 1, this type of color linear sensor comprises three sensor arrays 31R, 31G, 31B for three colors and transfer registers 32R, 32G, 32B disposed relative to the above sensor arrays 31R, 31G, 31B to thereby output signal charges of one line for every color in a line-sequential fashion.
FIG. 2 of the accompanying drawings shows a structure of another example of a conventional color linear sensor.
As shown in FIG. 2, this conventional color linear sensor is what might be called an R, G, B dot-sequential output type and includes a single sensor array 41 composed of R, G, B sensors arranged sequentially at the unit of pixels in a one-dimensional fashion and a single transfer register 42 opposed to the sensor array 41, thereby to output signal charges of respective pixels of one line simultaneously in a dot-sequential manner.
The above color linear sensor of line-sequential output type includes the three sensor arrays 31R, 31G, 31B so that, when these sensor arrays 31R, 31G, 31B scan an object upon copying or the like, they are displaced from each other in position, which needs many memories for correcting such displacement. Furthermore, the above color linear sensor of line-sequential type needs three output pins (terminals) corresponding to three colors, R, G, B, which needs extra circuits such as an analog-to-digital (A/D) converter or the like to effect the signal processing in the outside. There is then the disadvantage such that an external circuit becomes complicated in configuration.
On the other hand, the color linear sensor of dot-sequential output type having the single sensor array needs only a single output pin, which needs a single signal processing system. However, since the prior-art color linear sensor is of the dot-sequential output type, sensors of different colors are repeatedly arranged, i.e., a green signal component is output after a red signal component is output, a blue signal component is output after the green signal component is output and the next red signal component is output after the blue signal component is output, etc. As a result, the signal component of the adjacent sensor section is mixed into the signal component of the adjacent sensor section. This phenomenon will hereinafter be referred to as "color mixture". That is, this mixed signal component appears as a color mixture on a picture after signal charges are transferred and deteriorated by the transfer register 42. Thus, it is desirable that the color mixture in the sensor section is eliminated as much as possible. Therefore, in the manufacturing process of color linear sensors, a degree with which the color mixture occurred in the sensor section must be measured and respective sections of the color linear sensor must be adjusted in accordance with the measured degree of the color mixture.